Method of shaping a thin-walled body

ABSTRACT

A method of shaping a body includes putting a preform into a mold and heating the assembly to produce and increase pressure within the preform causing the preform to expand and conform to the shape of the interior of the mold.

United States Patent [72] Inventors Walter B. Dean Narberth; Harry P. Schane, Both (c/o The Budd Company 250 l-luntng Park Ave. Philadelphia, Pa. 19132), Lafayette Hill, Pa

211 Appl.No.. 803,403 22 Filed Mar. 10, 1969 [45] Patented Mar. 23, 1971 [54] METHOD OF SHAPING A THIN-WALLED BODY 4 Claims, 3 Drawing Figs.

[52] U.S. Cl 72/62, 72/367, 29/421 [51] Int. Cl B2ld 26/04 [50] Field ofSearch 72/60, 61, 62, 364, 367; 29/421 Primary Examiner-Richard J. Herbst Attorneys-Thomas I. Davenport, Edward M. Farrell,

John B. Sowell, Alford L. Trueax, Jr. and William R. Nolte ABSTRACT: A method of shaping a body includes putting a preform into a mold and heating the assembly to produce and increase pressure within the preform causing the preform to expand and conform to the shape of the interior of the mold.

pmsmznmzslsn I I 35721073 40 INVENTORS WALTER B. DEAN BY HARRY P. SGHANE @m/fzM ATTORNEY METHOD OF SHAPING A'THIN-WALLED BODY This invention relates to a method for shaping a container or body from a first shape, commonly calledra preform, to a final shape. More particularly, it relates to preforrns having relatively thin walls of high strength at ambient temperatures but with a lower strength and increased elongation at elevated temperatures.

Numerous different methods have been employed for forming bodies from preformed bodies. Blow and injection molding have been employed within a preform was filled with a liquid with the liquid being subjected to pressure to' cause the prefomi to expand until it contacts the wall of the mold. Other methods have employed stretch-forming operations which have included the forming of sheet metal blanks into a variety of different contoured shapes by pulling the blank either around a male-forming member to conform the blank to the latter or while the blank is betweena set of male and female dies of a contour to provide a desiredcurvature. Still other methods have employed electromagnetic forming, explosive forming and the like. 7 a

It is well known that extreme and unusual material requirements have been imposed in many applications involving high operational temperatures and speeds. Manyof the materials used to meet these requirements are not capable of being fuially formed by many conventional methods of the types mentioned. Such materials as titanium, ticonium, hafnium, beryllium and numerous other types of metal present particular problems in final forming. These materials can generally not be handled by conventional procedures at room temperatures because they are brittle and do not permit forming pres sure to be applied thereto without cracking.

These so-called high-strength metals generally have low elongation at room temperature and are capable of retaining good strength and good elongation at elevated temperatures. While explosive forming has been reasonably successful in some cases, it has not been an ideal method of final forming and in some locations its use is restricted.

It is an object of this invention to provide a novel method of fonning thin-walled bodies into irregular shapes.

It is a further object of this invention to provide an improved economical method of forming a thin-walled irregularly shaped body from a preform.

in accordance with the present invention, a method of shaping a thin metallic bodycomprises the steps of first providing a preform of the body to be shaped. The preform is'completely enclosed to retain pressure except for the opening adapted to be connected to a source of gas. A mold having an interior surface shaped to the form to which the metallic body is to be shaped is then provided with the preform being inserted into the mold. Gas is fed into the interior of the enclosed preform through the opening and pressurized to some predetermined pressure within the preform. The mold and preform are heated to increase the gas pressure within the preform causing it to expand and conform to the shape of the interior surface of the mold as the material being formed is reduced in strength and its elongation is increased as the temperature is increased.

This may be considered a special method of creep forming.

Other objects and advantages of the'present invention will be apparent and suggest themselves to those skilled in the art, from a reading of the following specification and claims in conjunction with the accompanying drawing, in which:

FIG. 1 is a view of a metal preform to be formed into an irregular shaped body, in accordance with the present invention;

FIG. 2 is a cross-sectional view of a mold and a metal preform illustrating the method of forming an irregular shaped body, in accordance with the present invention; and

H6. 3 is a side view of the body after it has been formed, in accordance with the present invention.

Referring particularly to FIG. 1, a cone-shaped metallic preform 10 is illustrated. The ends of the preform are joined with a continuous weld 12 after the metal has been cut to a suitable shape or may be mechanically joined to the preform to retain pressure. The metal may be titanium or other type metal normally hard to form with conventional methods. The

preform l isillustrated as being conical in shape and open a plate 18. The plates'l6 and 18 are welded or mechanically attached to the preform 1 0 to form a good seal. An opening 20 is provided in the top platel 6 with a conduit 22 being welded to the opening to'permit' to'be delivered to the interior of the preform l0.

The mold 14 includes a relatively thick metallic sizing die 24. A relatively thick metallic cover 26 is bolted or otherwise suitably mounted to the sizing die 24 prior to the forming operation, to be described.

An opening is provided in the cover 26 to permit the conduit 22 to pass therethrough. The conduit may be connected to a suitable source of gas (not illustrated). A valve 28 is provided to open or close the path between the source of gas and the interior of the preform l0.

The interior-wall of the mold 30 is shaped in accordance with the final form desired. In the embodiment illustrated, the interior wall includes top section 30 as well as smaller sections 32, 34 and 36. It is apparent that the interior of the mold may be of any shape desired.

The sizing die 24 includes a plurality of bleed holes 38, 40, 42 and 44. These bleed holes are provided to permit any trapped air within the mold 14 to escape as the preform 10 is expanded in a manner to be described. After the preform 10 has been inserted into the mold 14, an inert gas, which for example may argon, is delivered from a gas source, through the open valve 28, through the conduit 22 and into the interior of the preform. After the gas has been delivered and is at about 5Q p.s.i., the valve 28 is closed.The exact pressure applied depends upon the metal thickness and its physical properties. in the embodiment illustrated, the thickness may be between .010 and .016 inch, for example.

The mold assembly is then put into an oven where it is heated. The entire mold assembly is heated to approximately 1,200 F. At this point the pressure within the preform l0 rises toapproximately p.s.i. At the same time, the relatively high temperature causes the walls of the preform to become more formable. As a result of the combined action of the high pressure and greater formability of the metal at increased temperatures, the preform l0 expands until the thin walls make intimate contact with the interior walls of the mold.

The air between the preform and the mold is relieved through the bleed holes 38, 40, 42 and 44. After the preform 10 has been expanded, the mold is taken out of the oven and permitted to cool. Upon completion of the forming of the article, the top cover 26 is taken off the sizing die 24 and the formed body then taken out of the mold and is shaped as illustrated in FIG. 2. The top and bottom plates 16 and 18 are then removed from the formed article along with the conduit 22.

In some cases the gas pressure within the preform may be varied during the time that the preform is being heated. Also,

at some point, the pressure may be maintained at some.

predetermined level. Such means for varying and controlling the gas pressures at different times during the operation are well known and therefore are not illustrated or described in detail.

It is seen that the subject invention makes it possible to form containers or other bodies of irregular shapes in a relatively simple manner without cumbersome machining or explosives. Also, the initial preparations and final formation of the part is minimized.

We claim:

1. A method of shaping a thin metallic body comprising the steps of providing a preform of said body to be shaped, completely enclosing said preform except for an opening adapted to be connected to a source of pressurized gas, providing a mold having an interior surface shaped to the form to which said metallic body is to be shaped, inserting said prefonn into said mold, delivering a predetermined amount of said pressurized gas into the interior of said enclosed preform through said opening, closing said opening and maintaining said gas under a fixed pressure within said preform, heating said preform to cause the gas to expand to increase the pressure within said container causing said preform to expand and conform to the shape of the interior surface of said mold.

2. A method as set forth in claim 1 wherein the additional step is provided of relieving any trapped air between said prefonn and the interior surface of said mold during the expansion of said preform. 

1. A method of shaping a thin metallic body comprising the steps of providing a preform of said body to be shaped, completely enclosing said preform except for an opening adapted to be connected to a source of pressurized gas, providing a mold having an interior surface shaped to the form to which said metallic body is to be shaped, inserting said preform into said mold, delivering a predetermined amount of said pressurized gas into the interior of said enclosed preform through said opening, closing said opening and maintaining said gas under a fixed pressure within said preform, heating said preform to cause the gas to expand to increase the pressure within said container causing said preform to expand and conform to the shape of the interior surface of said mold.
 2. A method as set forth in claim 1 wherein the additional step is provided of relieving any trapped air between said preform and the interior surface of said mold during the expansion of said preform.
 3. The invention as set forth in claim 2 wherein the additional step is provided of enclosing said preform by applying a plate with an aperture therein to close an open area of said preform to form a gastight enclosure.
 4. The invention as set forth in claim 3 wherein a two-piece mold is provided with one of the pieces being provided with an opening to permit said pressurized gas to be delivered from said source through said opening and through the aperture of said plate into said enclosure. 